Biomedical subjects

L Cherry

Publications and source records attributed to L Cherry.

10 recordsLinked to original sources

PubMed2000

Spin label EPR structural studies of the N-terminus of alpha-spectrin.

Spectrin, a vital component in human erythrocyte, is composed of alpha- and beta-subunits, which associate to form (alphabeta)2 tetramers. The tetramerization site is believed to involve the alpha-spectrin N-terminus and the beta-spectrin C-terminus. Abnormal interactions in this region may lead to blood disorders. It has been proposed that both termini consist of partial structural domains and that tetramerization involves the association of these partial domains. We have studied the N-terminal region of a model peptide for alpha-spectrin by making a series of double spin-labeled peptides and studying their dipolar interaction by electron paramagnetic resonance methods. Our results indicate that residues 21-42 of the N-terminus region exhibit an alpha-helical conformation, even in the absence of B-spectrin.

Biopolymers↗

PubMed2000

Flexibility of the alpha-spectrin N-terminus by EPR and fluorescence polarization.

The structure and flexibility of the biologically important alpha-spectrin amino terminal region was examined by the use of fluorescence and EPR spectroscopy. The region studied has been previously demonstrated to be essential for the alpha-spectrin:beta-spectrin association of the tetramerization site. Appropriate spectroscopic probe moieties were coupled to this region in a recombinant fragment of human erythroid alpha-spectrin. There was good agreement between the EPR and fluorescence techniques in most of this region. Mobility determinations indicated that a portion of the region was relatively immobilized. This is significant, since although predictive methods have indicated that this region should be alpha-helical, previous experimental evidence obtained on smaller synthetic peptides had indicated that this region was disordered. Observed rigidity appears to be incompatible with such a disordered state, and has important ramifications for the flexibility of this molecule that is so integral to its role in stabilizing erythrocyte membranes.

Amino Acid Motifs↗

PubMed1999

Interactions of the alpha-spectrin N-terminal region with beta-spectrin. Implications for the spectrin tetramerization reaction.

Spectrin of the erythrocyte membrane skeleton is composed of alpha- and beta-spectrin, which associate to form heterodimers and tetramers. It has been suggested that a fractional domain (helix C) in the amino-terminal region of alpha-spectrin (Nalpha region) bundles with another fractional domain in the carboxyl-terminal region of beta-spectrin (Cbeta region) to yield a triple alpha-helical bundle and that this helical bundling is largely responsible for tetramer formation. However, there are certain objections to assigning a preeminent role to this helical bundling in the tetramerization reactions. We prepared several recombinant peptides of alpha-spectrin fragments spanning only the Nalpha region (lacking the dimer nucleation site) and quantitatively studied their interaction with beta-spectrin. We found that a majority of the interactions were localized, as expected, in the Nalpha-helix C region but that there was also some contribution from the nonhomologous region. More importantly, the temperature and ionic strength dependence of this interaction in our model peptides was different from that in intact spectrin. We suggest that, although the regions involving the putative helical bundling in alpha- and beta-spectrin undoubtedly play a significant role in tetramerization, regions distal to the Nalpha-helix C region in spectrin are also involved in tetramer formation. Structural flexibility and lateral interactions may play a role in spectrin tetramerization.

Biopolymers↗

PubMed1995

Aging in adults with Down syndrome: report from a longitudinal study.

Changes in functioning related to aging were examined in 34 adults (14 females, 20 males) with Down syndrome who were 22 to 56 years of age. Changes in functioning over 3 to 4 years were examined, with age, IQ at entry into the study, and gender considered. Neither effects of age at entry nor change over time were significant, suggesting that changes related to aging in adults with Down syndrome were minimal. In contrast, IQ at entry had a significant effect on all performances, suggesting that any examination of aging must consider intellectual level. Results do not support the idea that adults with Down syndrome show rapid age-related declines in functioning apart from the occurrence of a progressive dementia such as Alzheimer's disease.

Adult↗

PubMed1994

Cation transport mediated by Na+,K(+)-adenosine triphosphatase in lymphoblastoma cells from patients with bipolar I disorder, their relatives, and unrelated control subjects.

In an investigation of cation transport in bipolar affective disorder, we have measured parameters related to Na+,K(+)-adenosine triphosphatase, the enzyme that carries out active transport of sodium and potassium, in lymphoblastoid cells cultured from patients with bipolar affective disorder, age-matched nonaffected family relatives, and unrelated control subjects. Patients had lower ion transport per cell and per transport enzyme site than did related or unrelated control subjects. The rate of transport per cell appeared higher in nonaffected relatives of patients than in unrelated control subjects, though this difference did not reach significance. These data suggest that abnormally regulated ion transport may be associated with bipolar affective disorder independently of clinical state.

Biological Transport, Active↗

PubMed1979